AIMOur previous studies showed that electroacupuncture (EA) could inhibited radiant heat induced pain and acute or chronic inflammatory pain in rats. In the present study, we observed whether EA with different frequencies could suppress neuropathic pain.

METHODSL5/L6 nerve ligation model was used to assess the effect of EA on neuropathic pain. Mechanical allodynia was represented by 50% withdrawal threshold, while cold-induced ongoing pain was detected by the number of paw lift in 5 min when the rat was put on a 5 degrees cold plate. Han's acupoint nerve stimulator (HANS) was connected to needles inserted into acupoints "jiaji" and "Zusanli" in both sides. The parameters were: (intensity: 0.5-1-2 mA, 10 min each; frequency 2 Hz or 100 Hz; pulse width: 0.6 ms for 2 Hz, 0.2 ms for 100 Hz).

RESULTSEA of both 2 Hz and 100 Hz could relieve the mechanical allodynia, where 2 Hz could induce the effect with shorter latency; they could also relieve the cold-induced ongoing pain, where the effect of 2 Hz outlasted the EA session by up to 48 h after repetitive stimulations over several weeks; a significant relieving effect on cold-induced ongoing pain could also be induced by needle insertion without stimulation.

CONCLUSIONEA could relieve neuropathic pain, the analgesic effect of 2 Hz EA is higher than 100 Hz EA.